1. Field of the Invention
This invention relates to electrical connectors and to methods for making such connectors.
2. The Prior Art
In our U.S. Pat. No. 3,858,958 we have disclosed electrical connectors and methods of making the connectors, which are suitable for interconnecting printed circuit boards, and which connectors include an elongate core of elastomeric material having a substantially constant cross-section; a plurality of thin flexible conductive members arranged in spaced mutually parallel formation along the core; each substantially perpendicular to the longitudinal axis thereof and extending at least partially around the core; and means for securing the conductive members upon the core.
The U.S. Pat. No. 3,858,958 also discloses a method of making such a conductor which includes the stages of forming a plurality of flexible thin-walled electrically conductive rings at spaced positions along and secured to a solid core of elastomeric material of constant cross-section. It is proposed to form the rings by etching them from a hollow cylinder into which the core has been introduced and previously bonded. The cylinder itself is produced by etching the interior wall of metallic tube initially having a wall thickness which is greater than the required wall thickness for the cylinder.
It has been found that the formation of such a connector involves an inherent possibility if not obtaining a sufficiently satisfactory bonding between the outermost surface of the core forming material and the metallic conductors. In addition, the etching of the tube interior was found to involve difficulties in respect of obtaining a high degree of uniformity, i.e. a true cylindrical inner surface.
In a further known proposal, namely in U.S. Pat. No. 3,638,163 it has been proposed to provide a resilient tube which can be Teflon or rubber. Electric conductors are provided on the tube surface by a printing operation. For example, etched foil contacts such as gold plated copper. This known form of connector involves the inherent difficulty of ensuring that the contacts are of uniform radial thickness over their whole length and also of ensuring that the overall width of the various contacts radially of the core is uniform. These difficulties stem from the fact that in the known system one is using as the reference surface (for what is a relatively difficult coating or plating process) a flexible radially compressible substrate which in the first place is not particularly suitable for a precision construction and secondly not particularly suitable for obtaining a permanent bond.
It has been found that the above discussed forms of connectors can be improved by modifying the method of producing the core.